The Astrophysical Journal Letters最新文献

{"title":"Discovery of Volatile Gas in the Giant Impact Disk Around the 150 Myr Old HD 23514","authors":"Kate Y. L. Su, Attila Moór, Chengyan Xie, Ilaria Pascucci, George H. Rieke, Ágnes Kóspál, Mark C. Wyatt, Péter Ábrahám, Luca Matrà, Zoe Roumeliotis and D. J. Wilner","doi":"10.3847/2041-8213/ade872","DOIUrl":"https://doi.org/10.3847/2041-8213/ade872","url":null,"abstract":"We report the discovery of CO2 gas emission around HD 23514, an F5V star in the ∼150 Myr old Pleiades cluster, hosting one of the rare giant-impact disks with unique mineralogy dominated by silica dust. We show that the dust feature remains stable over several decades, and that the submicron grains, which give rise to the ∼9 μm feature, are cospatial with the hot CO2 molecules within the sub-astronomical-unit vicinity of the star. Examining a Spitzer spectrum taken 15 yr earlier, we show that the CO2 emission was also present at 4.3σ significance. The existence of tiny silica grains and volatile gas requires special conditions to prevent the rapid loss caused by stellar radiation pressure and photodissociation. We explore several pathways explaining the observed properties and suggest that a past giant impact and/or stripping atmospheric event, involving large bodies with volatile content similar to carbonaceous chondritic material, can simultaneously explain both the silica and volatile emission. Our discovery provides an important context for the amount of volatiles that a newly formed planet or the largest planetesimals could retain during the giant impact phase in the early solar system evolution.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144622307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orbital Modulation of Gamma Rays up to 100 TeV from LS 5039","authors":"R. Alfaro, M. Araya, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, R. Babu, P. Bangale, E. Belmont-Moreno, A. Bernal, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, S. Coutiño de León, D. Depaoli, P. Desiati, N. Di Lalla, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, K. Engel, T. Ergin, C. Espinoza, K. L. Fan, K. Fang, J. A. García-González, H. Goksu, A. Gonzalez Muñoz, J. A. González, M. M. González, J. A. Goodman, S. Groetsch, J. P. Harding, S. Hernández-Cadena, I. Herzog, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, P. Hüntemeyer, S. Kaufmann, D. Kieda, A. Lara, J. Lee, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, M. Mostafá, M. Najafi, L. Nellen, M. U. Nisa, N. Omodei, E. Ponce, Y. Pérez Araujo, E. G. Pérez-Pérez, C. D. Rho, A. Rodriguez Parra, D. Rosa-González, M. Roth, H. Salazar,..","doi":"10.3847/2041-8213/ade760","DOIUrl":"https://doi.org/10.3847/2041-8213/ade760","url":null,"abstract":"Gamma-ray binaries are luminous in gamma rays, composed of a compact object orbiting a massive companion star. The interaction between these two objects can drive relativistic outflows, either jets or winds, in which particles can be accelerated to energies reaching hundreds of teraelectronvolts (TeV). However, it is still debated where and under which physical conditions particles are accelerated in these objects and ultimately whether protons can be accelerated up to PeV energies. Among the well-known gamma-ray binaries, LS 5039 is a high-mass X-ray binary with an orbital period of 3.9 days that has been observed up to TeV energies by the High Energy Stereoscopic System. We present new observations of LS 5039 obtained with the High Altitude Water Cherenkov (HAWC) observatory. Our data reveal that the gamma-ray spectrum of LS 5039 extends up to 200 TeV with no apparent spectral cutoff. Furthermore, we confirm, with a confidence level of 4.7σ, that the emission between 2 and 118 TeV is modulated by the orbital motion of the system, and find a 2.2σ hint of variability above 100 TeV. This indicates that these photons are likely produced within or near the binary orbit, where they can undergo absorption by the stellar photons. In a leptonic scenario, the highest energy photons detected by HAWC can be emitted by ∼200 TeV electrons inverse Compton scattering stellar photons, which would require an extremely efficient acceleration mechanism operating within LS 5039. Alternatively, a hadronic scenario could explain the data through proton–proton or proton–gamma collisions of protons accelerated to petaelectronvolt energies.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"266 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144603047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Element Nucleosynthetic Origins from Abundance Spatial Distributions beyond the Milky Way","authors":"Zefeng Li, Mark R. Krumholz, Anna F. McLeod, A. Mark Swinbank, Emily Wisnioski, J. Trevor Mendel, Francesco Belfiore, Giovanni Cresci, Giacomo Venturi and Jia-Lai Kang","doi":"10.3847/2041-8213/ade7fa","DOIUrl":"https://doi.org/10.3847/2041-8213/ade7fa","url":null,"abstract":"An element’s astrophysical origin should be reflected in the spatial distribution of its abundance, yielding measurably different spatial distributions for elements with different nucleosynthetic sites. However, most extragalactic multielement analyses of gas-phase abundances to date have been limited to small numbers of sight lines, making statistical characterization of differences in spatial distributions of elements impossible. Here we use integrated field spectroscopic data covering the full face of the nearby dwarf galaxy NGC 5253 sampled at 3.5 pc resolution to produce maps of the abundances of oxygen, nitrogen, and sulfur using independent direct methods. We find strong evidence for differences in the elements’ spatial statistics that mirror their predicted nucleosynthetic origins: the spatial distributions of oxygen and sulfur, both predominantly produced in core-collapse supernovae, indicate that initial injection occurs on larger scales than for nitrogen, which is predominantly produced by asymptotic giant branch stars. All elements are well correlated, but oxygen and sulfur are much better correlated with each other than with nitrogen, consistent with recent results for stellar abundances in the Milky Way. These findings both open a new avenue to test nucleosynthetic models and make predictions for the structure of stellar chemical abundance distributions.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144603049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Follow-up Exploration of the TWA 7 Planet–Disk System with JWST NIRCam","authors":"Katie A. Crotts, Aarynn L. Carter, Kellen Lawson, James Mang, Beth Biller, Mark Booth, Rodrigo Ferrer-Chavez, Julien H. Girard, Anne-Marie Lagrange, Michael C. Liu, Sebastian Marino, Maxwell A. Millar-Blanchaer, Andy Skemer, Giovanni M. Strampelli, Jason Wang, Olivier Absil, William O. Balmer, Raphaël Bendahan-West, Ellis Bogat, Rachel Bowens-Rubin, Gaël Chauvin, Clémence Fontanive, Kyle Franson, Jens Kammerer, Jarron Leisenring, Caroline V. Morley, Isabel Rebollido, Nour Skaf, Ben J. Sutlieff, Evelyn L. Bruinsma, Sasha Hinkley, Kielan Hoch, Andrew D. James, Rohan Kane, Dimitri Mawet, Michael R. Meyer, Skyler Palatnick, Marshall D. Perrin, Shrishmoy Ray, Emily Rickman, Aniket Sanghi and Klaus Subbotina Stephenson","doi":"10.3847/2041-8213/ade798","DOIUrl":"https://doi.org/10.3847/2041-8213/ade798","url":null,"abstract":"The young M star TWA 7 hosts a bright and near face-on debris disk, which has been imaged from the optical to the submillimeter. The disk displays multiple complex substructures such as three disk components, a large dust clump, and spiral arms, suggesting the presence of planets to actively sculpt these features. The evidence for planets in this disk was further strengthened with the recent detection of a point source compatible with a Saturn-mass planet companion using JWST/MIRI at 11 μm, at the location a planet was predicted to reside based on the disk morphology. In this Letter, we present new observations of the TWA 7 system with JWST/NIRCam in the F200W and F444W filters. The disk is detected at both wavelengths and presents many of the same substructures as previously imaged, although we do not robustly detect the southern spiral arm. Furthermore, we detect two faint potential companions in the F444W filter at the 2σ–3σ level. While one of these companions needs further follow-up to determine its nature, the other one coincides with the location of the planet candidate imaged with MIRI, providing further evidence that this source is a sub-Jupiter-mass planet companion rather than a background galaxy. Such discoveries make TWA 7 only the second system, after β Pictoris, in which a planet predicted by the debris disk morphology has been detected.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144603048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recurrent Cometary Activity Discovered on Quasi-Hilda Jupiter Family Comet 362P/(457175) 2008 GO98","authors":"Kennedy A. Farrell, Colin Orion Chandler, Chadwick A. Trujillo, William J. Oldroyd, Jarod A. DeSpain, Mark Jesus Mendoza Magbanua, Maxwell K. Frissell and Phineas Stone","doi":"10.3847/2041-8213/addbd8","DOIUrl":"https://doi.org/10.3847/2041-8213/addbd8","url":null,"abstract":"We report the discovery of recurrent activity on quasi-Hilda comet (QHC) 362P/(457175) 2008 GO98. The first activity epoch was discovered during the perihelion passage of 362P in 2016, so we were motivated to observe it for recurrent cometary activity near its next perihelion passage (UT 2024 July 20). We obtained observations with the Lowell Discovery Telescope, the Astrophysical Research Consortium telescope, and the Vatican Advanced Technology Telescope and identified a second activity epoch when 362P had a true anomaly (ν) as early as 318 1. We conducted archival searches of six repositories and identified images obtained with Canada–France–Hawaii Telescope MegaCam, Dark Energy Camera, Pan-STARRS 1, SkyMapper, Zwicky Transient Facility, and Las Cumbres Observatory Global Telescope network data. Using these data, we identified activity from a previously unreported time span, and we did not detect activity when 362P was away from perihelion, specifically 83∘ < ν < 318∘. Detection of activity near perihelion and absence of activity away from perihelion suggest thermally driven activity and volatile sublimation. Our dynamical simulations suggest 362P is a QHC, and it will remain in a combined Jupiter-family comet (JFC) and quasi-Hilda orbit over the next 1 kyr though it will become increasingly chaotic nearing the end of this timeframe. Our reverse simulations suggest 362P may have migrated from the orbit of a long-period comet (∼53%) or Centaur (∼32%); otherwise it remained a JFC (∼15%) over the previous 100 kyr. We recommend additional telescope observations from the community as 362P continues outbound from its perihelion on UT 2024 July 20, as well as continued observations for a third activity epoch.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144593960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas-poor Hosts and Gas-rich Companions of z ≈ 3.5 Radio Active Galactic Nuclei: ALMA Insights into Jet Triggering and Feedback","authors":"Wuji Wang, 无忌 王, Carlos De Breuck, Dominika Wylezalek, Matthew D. Lehnert, Andreas L. Faisst, Andrey Vayner, Nicole Nesvadba, Joël Vernet, Pranav Kukreti and Daniel Stern","doi":"10.3847/2041-8213/ade675","DOIUrl":"https://doi.org/10.3847/2041-8213/ade675","url":null,"abstract":"Cold gaseous systems play important roles in galaxy evolution by possibly providing fuel to ignite active galactic nuclei (AGN) activity and star formation. In this work, we analyze [C ii]158 μm and continuum observations from the Atacama Large Millimeter/submillimeter Array for a sample of four radio AGN at z ≈ 3.5, focusing on eight associated companion cloud systems discovered within projected distances of tens of kiloparsecs or less. The spatial distribution of these companions indicates that the majority of cold gas is not located at the AGN position, i.e., not in their host galaxies. With the assistance of [C ii] at 0 2 resolution, we further confirm the gas-poor nature of the hosts by reanalyzing archival [C i] (a tracer of H2) at ∼2″ resolution. Our sample has [C ii] luminosities in a range of 2.8 × 108 < L[C II]/L⊙ < 4.2 × 109. The L[C II]/LIR ratio, ∼9.4 × 10−4, is consistent with sources discussed in the literature. Our findings show the gas-poor radio AGN hosts have nearby gas-rich companions. We propose that these companions may be stripped clouds resulting from merger processes, which could be a trigger of radio-loud AGN. They may also be a signature of negative AGN feedback (e.g., shock heating) on these infalling companions and on the host galaxy. In general, our analysis shows that powerful AGN at and before Cosmic Noon are impacting and being impacted by cold gaseous clouds in their circumgalactic or protointracluster media.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144593962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discovery of Diffuse Radio Emission in a Massive z = 1.709 Cool Core Cluster: A Candidate Radio Minihalo","authors":"Julie HLavacek-Larrondo, Roland Timmerman, Christoph Pfrommer, Erik Osinga, Larissa Tevlin, Tracy M. A. Webb, Natalia Martorella, Xiaoyuan Zhang, Reinout van Weeren, Hyunseop Choi, Gabriella Di Gennaro, Marie-Lou Gendron-Marsolais and Carter Rhea","doi":"10.3847/2041-8213/add527","DOIUrl":"https://doi.org/10.3847/2041-8213/add527","url":null,"abstract":"Clusters of galaxies host spectacular diffuse radio sources, extending over scales from 100 kpc to several Mpcs. These sources, with extremely faint surface brightness (μJy/arcsec2 level), are not tied to individual galaxies but trace synchrotron emission from large-scale magnetic fields and relativistic particles within the intracluster environment. Here, we report the discovery of a candidate radio minihalo in SpARCS104922.6+564032.5, the most distant cool-core galaxy cluster identified to date at z = 1.709, using deep LOFAR 120–168 MHz observations. We show that this emission originates from diffuse cluster-associated processes rather than unresolved active galactic nuclei or star-forming galaxies. The diffuse radio emission coincides spatially with the X-ray emission of the hot intracluster medium and has a radio power of W Hz−1, exhibiting striking similarities to low-redshift radio minihalos. This discovery doubles the redshift of previously known minihalos, challenging models of inverse Compton losses and indicating the presence of strong magnetic fields, enhanced turbulence in high-redshift clusters, or active hadronic processes that require a cosmic-ray-to-thermal-energy ratio of 0.07 within 200 kpc, assuming a clumped distribution with spatial correlations among the gas, cosmic rays, and magnetic field that partially compensate for cosmological redshift dimming. It further implies that magnetic fields are efficiently amplified to ∼10 μG levels within an Mpc3 volume during the epoch of cluster formation before z ∼ 2. These findings provide critical insights into high-redshift cluster physics and emphasize the transformative potential of next-generation radio surveys, such as those with the Square Kilometre Array and next-generation Very Large Array (ngVLA), in exploring the early evolution of galaxy clusters.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"149 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144603050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Hα Line as a Probe of Chromospheric Magnetic Fields","authors":"Harsh Mathur, Jayant Joshi, Thore Espedal Moe, Tiago M. D. Pereira and K. Nagaraju","doi":"10.3847/2041-8213/ade8ea","DOIUrl":"https://doi.org/10.3847/2041-8213/ade8ea","url":null,"abstract":"We explore the diagnostic potential of the Hα line for probing the chromospheric magnetic field using a realistic 3D radiative magnetohydrodynamic (rMHD) model. The Stokes profiles of the Hα line are synthesized through full 3D radiative transfer under the field-free approximation, alongside the Ca ii 8542 Å and Fe i 6173 Å lines for comparison. The line-of-sight (LOS) magnetic fields are inferred using the weak-field approximation for the Hα and Ca ii 8542 Å lines, while the Fe i 6173 Å line is analyzed through Milne-Eddington inversion techniques. The comparison between the inferred LOS magnetic field maps and the magnetic fields in the rMHD model revealed that the Hα line core primarily probes the chromospheric magnetic field at = −5.7, which corresponds to higher layers than the Ca ii 8542 Å line core, which is most sensitive to conditions at = −5.1. On average, the Stokes V profiles of the Hα line core form 500 km higher than those of the Ca ii 8542 Å line core. The Hα polarization signals persist after adding noise, and with noise at the level of 10−3Ic, most simulated magnetic structures remain visible. These findings suggest that spectropolarimetric observations of the Hα line can provide complementary insights into the stratification of the magnetic field at higher altitudes, especially when recorded simultaneously with widely used chromospheric diagnostics such as the Ca ii 8542 Å line.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144593961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-instrument Search for Gamma-Ray Counterpart of X-Ray Transients Detected by EP/WXT","authors":"Yan-Qiu Zhang, Wang-Chen Xue, Jin-Peng Zhang, Ce Cai, Shao-Lin Xiong, Cheng-Kui Li, Yuan Liu, Chen-Wei Wang, Hao-Xuan Guo, Shuo Xiao, Wen-Jun Tan, Chao Zheng, Jia-Cong Liu, Sheng-Lun Xie, Peng Zhang, Wen-Long Zhang, Yue Wang, Zheng-Hang Yu, Yang-Zhao Ren, Ping Wang, Yue Huang, Xiao-Bo Li, Xiao-Yun Zhao, Shi-Jie Zheng, Zhen Zhang, Shu-Xu Yi, Li-Ming Song and Shuang-Nan Zhang","doi":"10.3847/2041-8213/ade0aa","DOIUrl":"https://doi.org/10.3847/2041-8213/ade0aa","url":null,"abstract":"As a soft X-ray imager with an unprecedentedly large field of view, Einstein Probe (EP)/Wide-field X-ray Telescope (WXT) has detected many (fast) X-ray transients, whose nature is very intriguing. Whether there is a gamma-ray counterpart for the X-ray transient provides important implications for its origin. Some of them have been reported to be associated with gamma-ray bursts; however, a systematic study on the gamma-ray emission of these X-ray transients is lacking. In this work, we implemented a comprehensive targeted search for gamma-ray counterparts to 63 X-ray transients reported by EP/WXT during its first year of operation, using the dedicated multiple-instrument search pipeline, Energetic Transients Joint Analysis System for Multi-Instrument (ETJASMIN), with GECAM-B, GECAM-C, Fermi/GBM, and Insight-HXMT data. We find that 14 out of 63 (22%) EP/WXT X-ray transients have gamma-ray counterparts. For other transients, the ETJASMIN pipeline provided the upper limit of the gamma-ray emission, which is more stringent than that given by an individual instrument. Moreover, we investigated the properties of the X-ray transients and their gamma-ray counterparts and explored the relation between the X-ray transient and the gamma-ray counterpart.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144593963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Clues on the Extended He ii Ionization in IZw18 from GTC/MEGARA and JWST/MIRI","authors":"A. Arroyo-Polonio, C. Kehrig, J. M. Vílchez, J. Iglesias-Páramo, E. Pérez-Montero, S. Duarte Puertas, J. Gallego and D. Reverte","doi":"10.3847/2041-8213/ade874","DOIUrl":"https://doi.org/10.3847/2041-8213/ade874","url":null,"abstract":"IZw18 is one of the lowest-metallicity star-forming galaxies known at z ∼ 0, considered a unique local analogue of the first galaxies. The origin of its hard ionizing continuum, expected to be a common feature in the early Universe and traced by He ii emission lines, remains intensely debated and challenging to explain. Here we combine optical Gran Telescopio Canarias MEGARA and mid-infrared (JWST/MIRI) integral field spectroscopic observations for IZw18 to shed new light on the high-ionization phenomenon. This Letter reports the first detection of the high-ionization [Ne v]14.32 μm line in IZw18. Its emission is spatially extended and coincident with the He ii peak, revealing the presence of highly energetic ionizing sources that surpass mechanisms previously proposed on the basis of He ii alone. Our kinematic studies highlight that the He iiλ4686-emitting gas displays higher velocity dispersions and a different velocity pattern compared with the Hβ emission, suggesting the presence of energetic processes such as shocks or stellar-driven feedback. Additionally, integrated spectra show asymmetric blueshifted profiles in the He iiλ4686 line, possibly indicating early-stage stellar-driven outflows potentially facilitating future ionizing photon leakage. Our spatial analysis also reveals differences in structure between the emission of Hβ and He iiλ4686, with the He iiλ4686 peak offset by a projected distance of 140 pc from the peak Hβ emission. This indicates distinct locations for the most extreme ionizing sources compared to moderate ionizing sources. Our findings underscore the complex interplay of physical processes in extremely metal-poor environments with highly ionized gas, offering new insights into the conditions prevailing in the early galaxies.","PeriodicalId":501814,"journal":{"name":"The Astrophysical Journal Letters","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144586553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}